On 2025-08-19 01:46:10 [+0900], Yunseong Kim wrote:

Hi everyone,

Hi,

 {
     ...
     local_bh_disable();
     spin_lock(&bhead->lock);
     spin_lock(&bhead2->lock);
     ...
 }

The sequence local_bh_disable() followed by spin_lock(), In a PREEMPT_RT
enabled kernel, spin_lock() is replaced by a mutex that an sleep.
However, local_bh_disable() creates an atomic context by incrementing
preempt_count, where sleeping is forbidden.

As Eric said, the mentioned pattern is common and not problematic.
The wrong assumption here is that local_bh_disable() on PREEMPT_RT
"creates an atomic context by incrementing preempt_count, where sleeping
is forbidden". This is simply not the case.

Best regards,
Yunseong Kim

Sebastian